Copies of the DJ Hero 2turntable bundle or "Party Bundle" from Gamestop will include the Puma turntable bag seen above. As far as pre-order bonuses go, this is basically a win-win for Activision, Gamestop, and you (probably Puma as well).
Gallery: DJ Hero 2 (puma bag pre-order) | 1 Photos
How? Gamestop gets an exclusive item to tempt purchasers away from other retailers, you get a nice-looking bag, and Activision now has a built-in mechanism to encourage DJ Hero fans to take the game to other people's houses and spread the message of DJ Hero.